1. Field of the Invention
This invention relates to improvements in animal feeds. More particularly, the invention relates to improvements in the utilization of feed by dairy cows.
2. Description of the Prior Art
It is well known that the amino acids in orally fed proteins are largely degraded to ammonia by rumen microorganisms. The ammonia so evolved is then reconstituted into the specific amino acids needed to synthesize and multiply protein, mostly in the form of bacteria. Thus, the proportion of the various amino acids in feed proteins and that in the ruminally synthesized protein is often distinctly different. In some cases the biological value of the synthesized protein is superior to that of the feed protein; on the other hand, the reverse is often true. In effect, the type of synthesis that occurs in the ordinary rumen function tends to convert all feed proteins to a common mould. Although the supply of methionine in this common mould may be adequate for the gestating or fattening animal, it is deficient for the maximum performance of fast-growing young animals, high-wool producing sheep or high-milk producing dairy cows.
In the case of the dairy cow, methionine plays an important role in lipid metabolism in addition to its contribution to milk protein formation. At the time of freshening, the high-producing cow cannot supply from feed alone all the nutrients needed for maximum milk production, and must draw heavily on body stores, especially body fat deposits. Methionine is the major chain initiator in lipo-protein synthesis, the mechanism by which body fats are mobilized and transported to the mammary gland. Thus, at the peak of production the cow has multiple needs for a single nutrient that is produced by the rumen in limited quantities. Increasing the oral supply of methionine, subject to attack in the rumen, has no effect on the amount available to the cow itself. However, the use of methionine analog instead of the preformed amino acid has been found to result in greater methionine availability as indicated by elevated methionine blood levels in analog-fed cows.
There are many published articles in technical journals on the effects of methionine hydroxy analog such as the article of L. C. Griel, Jr. et al. "Milk Production Response to Feeding Methionine Hydroxy Analog to Lactating Dairy Cows", Journal of Dairy Science, Vol. 51, No. 11, pages 1866-1868. However, in terms of weekly production of 4% fat-corrected milk, only about a 5% increase in milk production was obtained with a feeding of 40 g analog per day and an increase of about 9% with a feeding of 80 g analog per day. In other words, the yield increases were fairly limited when compared with the increased feeding costs associated with these quantities of the methionine hydroxy analog.
Other studies such as Bishop, "Methionine Hydroxy Analogue Supplementation in Beef and Dairy Cattle", Feedstuffs, Vol. 43, No. 5, p. 31, again show only limited yield improvements by the feeding of the methionine hydroxy analog with, for instance, a yield increase of less than 11% with the best candidates, i.e. first-calf heifers during early lactation. In older cows after several lactations the response to the analog generally decreased. The material known as "methionine hydroxy analog" is 2-hydroxy-4-(methylthio) butyric acid.
It is, therefore, the object of the present invention to provide an aminal feed containing methionine hydroxy analog which will provide improved milk yield as compared to the previously known methionine hydroxy analog feed additives.